Thread grinding machine



July 1, 1947. F. TURRETTINI 2,423,422

THREAD GRINDING MACHINE Filed March 27, 1945 5 sheets-sheet 1l mmm, mmQN QW E July 1, 1947. F. TURRETTLNI THREAD GRINDING MACHINE Filed March27, 1945 3 Sheets-Shea? 2 July 1, 1947. F.-TURRETT|N| 2,423,422

TEREAD GRINDING MACHINE Filed March 27, 1945 5 Sheets-Sheet 3 Ilz/U@12:60.21 Twzr e tte/@ZL Patented July 1, 1947 UNITED STATES ATENTOFFICE THREAD GRINDING MACHINE Fernand Turrettini, Geneva, Switzerland,as-

sgnor to Societe Genevoise DInstruments De Switzerland, a Iirm ofPhysique, Geneva, Switzerland 6 Claims. l

The present invention relates to thread grinding machines, and inIparticular to machines of the type comprising a grinding wheel mountedon a carriage slidable at a right angle to the axis of the work pieceunder the action of a first adjusting device, a truing tool mountedretractably in front of the grinding wheel on a rst support mountedrotatively on said carriage around an axis parallel to the direction ofmotion of the latter, the grinding wheel being carried by a secondsupport mounted rotatively around the axis of rotation of the firstsupport and slidably along this common axis, and a second adjustingdevice inserted between the first and the second support for moving thegrinding wheel in a direction parallel to that of said carriage, withthe object that the distance from the cutting edge of the grinding wheelto the axis of the work piece remains permanently determined by theindications of the first adjusting device, independent from the quantityof abrasive removed from the grinding wheel.

The advantage of this machine is that the operator can carry on itsthread grinding work without the necessity of frequently interrupting itfor measuring the workpiece, the micrometric adjustment of the wheelsupporting carriage giving always an accurate reading of the position ofthe wheels cutting edge in respect with the workpiece, independentlyfrom the wear of the wheel.

The annexed drawing represents by way of example one constructional formof the machine according to the invention.

The machine according to the invention, of the type mentioned above,eliminates all these diiculties. It is characterized in that the truingdevice, which operates in front of the grinding wheel, is retractablyarranged on a first support enabling to clear the grinding Wheel, saidsupport being borne by a carriage in such a manner as 'to be dependenton the latter in the direction of the travel of this carriage and, inthe same time, rotating on itself in order to adjust the inclination ofthe plane in which the truinghas to be performed, the grinding wheelbeing carried by a second support concentric with the first one andarranged to rotate on itself in such a manner that the grinding wheelmay be adjusted tangentially to the helices of the thread to be groundand that it also may move in a direction parallel axis ci the work pieceremains permanently determined by the indications of the first adjustingdevice, independent from the quantity of abrasive removed from thegrinding wheel.

The annexed drawing represents by way of example one constructional formof the machine according to the invention. The Fig, l is a transversesection; the Fig. 2 is a section through II-II and the Fig. 3 a sectionthrough III-III of the Fig. l. The Fig. 4 is a front elevation.

In all these figures, I is the bed of the grinding machine comprising aslide 2 extending at right angle to the longitudinal slides 3 and 3a ofthe bed; the slide 2 extends towards the rear of the machine and bearsthe carriage 4. The table is and the axis of the work piece to be groundis the work piece itself being 6. The work piece moves with the table onthe bed by means of the spindle 1, as well as by means of other membersnot shown.

The grinding wheel is 8, its axis is 9; the latter is being driven bythe pulley I0. The truing diamond is II, its point of contact with thegrinding wheel is on the horizontal axis A-A at right angle to the axisof the Work piece to be ground and passing through the centre of thegrinding wheel. The arm I2, carrying the diamond, is fixed on trunnion-pin I3. The diamond II trues-up the two anks of the active face of thegrinding wheel by an oscillatory movement of small amp-litude about saidtrunnion pin. The oscillatory movement is produced by means not shown onthe drawing.

IThe trunnion pin I3 revolves in a head Ill dependent on a shaft I5which may, by rotating in a bearing Iii, describe the angle a comprisedbetween the flanks of the active face of the grinding wheel. The bearingI formspart of an arm i? rigidly fixed by screws IS and I9 on extensions28 and 2l of a hollow cylinder 22 rotating in bearings 23 and 24belonging to a sleeve 25 iixed to the carriage 4.

This rotary motion, obtained by the action of a worm screw 26 engaging atoothed sector 26 fixed to the sleeve 25, serves to adjust the plane ofinclination in which the diamond I I has to carry out the truing-up. Theworm screw 25 rotates "i bearing 2l and 28 dependent on the arm Il. Thegroup consisting of pieces I6, Il, 2d, 2| and 22 forms the rst supportwhich moves with the carriage i with respect to the axis 6 and the workpiece t through the action of a handle 29 dependent on a graduated wheel36; the latter is fixed on a shaft 3I comprising at its extremity athreaded portion 32 engaged with the nut 33 dependent on the carriage 4.

A second support is arranged concentrioally with the hollow cylinder 22;it is formed by the tube 34 ending at the extremity facing the workpiece by a ange 35 xed rigidly on the tube and carrying the bearing 3Scontaining the axis 9 of the grinding wheel S. The tube 34 bears at itsrear a flange 31 on which is fixed the motor 38 driving the grindingwheel.

The second support 34 may rotate about the axis A--A under the action ofa toothed sector 33 with straight teeth engaging with a circular rackformed by a tube 4S provided with parallel grooves 4l showing theprofile of a rack.

The tube 45 is fixed axially on a shaft 42 on which it may freely rotatedue to the ball bearings li and 44. The shaft 4:2 may move axially bymeans of a screw l5 engaging with a not 46 fixed in a recess il on theshaft 42. The rotation of this screw is eifected by the action of awheel 43 provided with a handle 49 and with a graduation 55. The groupconsisting of pieces 39, 4I, 42, 55, 45, 49 and 55 has the object ofadjusting the grinding wheel tangentially to the helices of the threadto be ground on the piece 6. The tube 34 with all the pieces which itcarries (second support) has to move axially in the hollow cylinder 22(first support) in order to bring the grinding wheel 8 in contact withthe diamond ll in such a manner that the truing operation re-conditionsthe profile of the active edge of the grinding wheel. This axialmovement is obtained by means of a second adjusting device formed by ahandle 5| dependent on a shaft 52', meshing by the gear 53 with a shaft54, the bearing 54 of which is dependent on the arm il. The shaft 54transmits its rotary motion to the gear 55 by means of universal joints56 and 5l. The shaft of the gear 55 is provided with an extensible part55a to allow for the rotation of support 34 around the axis A-A. Therotation of 55 drives the pinion 58 dependent on a screw 59 forming partof a shaft 5D, which is supported on one hand by a bearing 5l fixed aswell as the nut 62 on the flange 31 and consequently on the tube 34 andthe grinding wheel 3 which it carries, and on the other hand, by a ballbearing 53 arranged in a piston IB4 which moves in the tube 34 andresting at 65 on a rod 55 housed 67 and 68 in the hollow cylinder 22.

A spring 69 thrusting on one hand on a circular abutment li! arranged torotate in the piston G4, and, on the other hand, on a lid 1I xed to thetube 34, constantly forces the grinding wheel towards the diamond. Theadjusting screw 59 is opposed to the pressure exerted by the springbecause it indirectly thrusts on the hollow cylinder 22, which is fixedaxially. The rotation of the shaft B0 thus enables bringing the grindingwheel in contact with the diamond.

It is by no means necessary that the amplitude of the travel imparted tothe grinding wheel by the second adjusting member to be taken intoconsideration, measured or checked in any way in a machine workingaccording to the invention. This travel may be of any length, providedthat it is sufficient to bring again the profile of the grinding wheelinto contact with the diamond in such a manner that the action 0f thelatter reconditions the surface of the grinding wheel.

The second support 34 has therefore to rotate and to slide in the iirstcylinder 22; it is important that these movements are effected with aminimum of friction in order not to reduce the sensibility of theadjustments. For this reason, the sets of balls 12 and T3 insertedbetween the hollow cylinder 22 and the tube 34 have to support and toguide the latter, the balls being able to roll in all directionsenabling said pieces to carry out relativerotary and translatorymovements. The sets of balls are arranged at the two extremities of thetube 34 and are formed by `two elements im and 72b (for the train 12)separated from each other by an angle b suiciently large to decomposethe weight P of the tube 34 into two divergent components P1 and P2which prevent any de-centrmg movement in the direction B-B. Thisarrangement of balls produces an eect similar to that of usual prismaticguide ways and has the advantage of enabling movements with a minimum offriction. The arm I2, which carries the diamond Il, may carry out anadditional rotary motion about the trunnion pin I3 and thus may bebrought into the retracted position when not in use, as shown on Fig. 4,in which position it enables the grinding wheel to come freely intocontact with the work piece to be ground. The arm l2 may be maintainedin this position by a retaining member 55.

If it is required to grind threads or taps, the axis C-C has to bevertically adjusted by means of the worm screw 25. Ii, on the otherhand, milling cutters for gears have to be ground, where thecharacteristic profile is to be at right angle to the helices, the axisC-C has to be maintained in the same plane as that of the grinding wheel8, plane which is tangent to the helices of the work piece to be ground.This result will be obtained by means of the worm screw 25 and therotating rack 4).

The machine described enables maintaining the active edge of thegrinding wheel immobile in space during the operation of truing-upcarried out by a tool borne on a slide, the distance of which from theaxis of the work piece being constantly controlled by means of anadjusting member 29, 3), dependent on the bed of the machine. The truingtool acts at the point of contact of the grinding wheel with the workpiece, so that a definite relation of the position of the slide withrespect to the axis of the work piece, when the latter will reach theprescribed dimensions, may be ensured. This relation will be given bythe adjusting member mentioned above.

The movable parts Il, l2 of the truing member, which may form anobstable to the Contact of the work piece with the grinding wheel, maybe retracted in order to permit such a contact.

Thus, the machine described does away with the necessity of measuringthe work piece during the grinding operation; it further makes it possible to grind either threads with the characteristic profile being in aplane containing the axis of the work piece (in the case of screws andtaps) or in a plane at right angle to the helix of the thread (in thecase of gear milling cutters).

What I claim is:

1. A thread grinding machine comprising a grinding wheel mounted on acarriage slidable at a right angle to the axis of the work piece underthe action of a first adjusting device, a truing tool mountedretractably in front of the grinding wheel on a first support mountedrotatively on said carriage around an axis parallel to the direction ofmotion of the latter, the grinding wheel being carried by a secondsupport mounted rotatively around the axis of rotation of the firstsupport and slidably along this common axis, and a second adjustingdevice inserted between the rst and the second support for moving thegrinding wheel in a direction parallel to that of said carriage, withthe object that the distance from the cutting edge of the grinding wheelto the axis of the work piece remains permanently determined by theindications of the first adjusting device, independent from the quantityof abrasive removed from K the grinding wheel.

2. Machine according to claim 1, characterized in that the truing toolis carried by an oscillating arm mounted on the rst support in such amanner that it is possible to bring it into a retracted position by anoscillation of sufficient amplitude.

3. Machine according to claim l, characterized by the fact that thesecond support comprises cylindrical parts passing through a cylindricalbearing of the rst support, sets of balls being inserted at these spotsbetween the two supports in order to enable the second support to rotateand to travel axially in the rst one, without harmful friction, wherebythe grinding wheel can be inclined in accordance with the lead of thethread to be ground.

4. Machine according to claim l, characterized by four sets of ballsarranged by pairs at the extremities of cylindrical bearing surfacesbetween the first and the second support, the two sets of each pairbeing spaced apart from one another, in order to produce an eiTect ofprismatic guiding excluding all radial or lateral play of the secondsupport, by means of the action of its own weight.

5. Machine according to claim l, characterized by the fact that therotary motion of the second support is obtained by means of a toothedsector dependent on said second support and which is engaged with acircular rack rotating freely on a shaft carried by the rst support-andwhich may travel axially by means of an adjusting member, determiningthe angle comprised between the plane of the grinding wheel and that inwhich the truing-up is carried out.

6. Machine according to claim 1, characterized in that the secondsupport also carries the motor driving the grinding Wheel.

FERNAND TURRETTINI.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date y 1,564,670 Hanson Dec. 8, 19251,946,883 Tougas et al Feb. 13, 1934 2,087,662 Bysshe et al. July 20,1937 2,292,875 Flanders Aug. 11, 1942 2,311,253 Stewart Feb. 16, 1943

